Saponification of cellulose esters



- Io Drawing.

tion.

Patented Jan. 31, 1933 UNITED "STATES PATENT OFFICE cam DREYIUS, orimw Your, N. Y., am: WILLIAM wnnnnmn, or 0mm IIAND,-HABYLAND, ASSIGNQRS TO CELANESE GORPO BATION OF AMERICA, A 003! POBATION OF- DELAWARE This invention relates to the treatment of products made from orcontaining inorganic esters of cellulose and is directed particularly to an improved method of saponifymg such inorganic esters ofcellulose.

An object of this invention is to provide a process for vthe 'sa onificati n of inorganic cellulose ester materials whereby the valuable properties of the material will be enhanced.

Another object of this invention is to saponify the inorganic cellulose esters under. such conditions that a material of greatly increased strength is obtained.

Still another object of our invention is to render yarns, films, etc., containing inorganic esters of cellulose capable. of absorbing atmospheric humidity and becoming more suitable for working in textile operations.

Another object of this invention is to treat nitrocellulose in such a manner that its inflammability is greatly reduced but its .valuable properties are retained. Other ob jects. and advantages of this invention will appear from the following detailed descrip All of the saponification processes suggested to date have utilized an aqueous solution of an alkali or other material which would yield free hydroxyl ions in solution.

'This saponification treatment, however, was

objectionable since in addition to the great loss in weight, it resulted in the cellulose esters losing most of their distinctive and desirable properties such as strength, elasticity, hand appearance, etc. Also the saponification yielded a regenerated cellulose which material is rather weak in tensile strength. Moreover, with the old process it was difiicult to control the saponification so as to yield a product which'was uniform in ap earance and evenly saponified.

t was also lmown that nitrocellulose possessed some properties'which were very much desired in materials used for textile purposes. However, the 'use'of this particular ester of cellulose in the textile field has been practically nil because of its high inflammability and because the denitrating. processes heretofore employed have not only reduced its inflammability but at the same time adversely saromlcarion or cELLuLosE ns'rnns -.-App1icatlon fl1ed Iune a0, 1928. Serial No. 287,085. v

atiected the other valuable properties the nitrocellulose. Our invention has overcome this difliculty since it results in the saponification of thenitrocellulose without deleteriously affecting the properties which render 1t useful for textile purposes.

We have now found that if the saponification of the'cellulose-esters is. effected by introducing the ester or ester materials into an atmosphere of'or containing ammonia gas and water vapor, the product remaining dif-. fers in its progerties from that obtained by known saponi cation methods. of the saponification reaction is apparently changed and a greater degree of control of the reaction is permissible. By proper con- The nature trol of this method of saponification, it is possible to obtain a cellulose ester which will 1 not take cotton dyes. It is possible by this I method to effect avirtually complete saponification of the cellulose nitrate in a comparatively' short time. The cellulose which remains after such complete saponification.

possesses desirable qualities which are not found in regenerated cellulose.

The cellulose nitrate materials treated in accordance with this process possess another marked advantage, not only over materials saponified by other known methods but also ing its use for textile purposes. We find that nitrocellulose material which has been virtually completely saponified in accordance with this invention can be subjected to such temperatures as are usually utilized in ironing without any deleterious efiects upon the material. This desirable result is efi'ected by subjecting the nitrocellulose material to the action of an atmosphere of, or containing,

'a base and water vapor at comparatively low temperatures. Enough of the saponifying medium should be present to effect the desired amount of saponification.

The material to be treated can be in any desired form such as yarn or thread in hanks or on bobbins or pirns, in the form of knitted or woven fabric, garments or in the form of films, bristles, etc; The desired gaseous atmosphere can be obtained in any suitable manner for instance, by suspending the cellulose ester material in a large aspiratorconnected with a container having therein a 28% solution of ammonia or other volatile base.

Without desiring to be limited to such specific concentrations or particular reagents it can be stated that very good results were obtained by first extracting the cellulose ester material toremove any lubricants which might be present, drying the material at 100 C. and then subjecting the same to the action of an atmosphere saturated with ammonia and water vapor at temperatures of 2 5 C. to 30 C. The cellulose nitrate material was suspended in a large aspirator con-' nected with a flask containing an ammonia solution. The time during which the reaction is allowed to proceed will vary depending upon the extent of saponification desired. Thus at the end of 4 hours an approximate saponification of 2.5%. was found; at the end of 6 hours 10.1%; at the end of 8 hours 63.1%; at the end of 16 hours 99.8%. The time can be shortened by utilizing a slightly higher temperature for the reaction atmosphere but the lower temperatures are preferable since they resultin a more uniform saponification.

The materials which may be used to effect the saponification can be ammonium hydroxide, methyl amine, dimethyl amine or any other volatile base which will yield hydroxyl ions under the conditions of operation The base selected however, should be compatible-with water vapor since the latter must be present in the reaction atmosphere. As previouslystated, good results were obtained utilizing an aqueous solution of, ammonia of approximately 28% strength.

This process is applicable not only to yarns, threads, films, etc., made of or containing cellulose nitrate but also can be applied to such cellulose ester materials when they are admixed or formed with other fibres, whether the latter are animal, vegetable or artificial in nature. Thus a fabric containing cellulose nitrate in admixture with cotton, wool, silk, linen, reconstituted cellulose (rayon) can be effectively treated in accordance with this invention.

The fact that thecellulose remaining after complete saponification according to our invention is different from normally regenerated cellulose is further evidenced by the insaponified yarn. This indicates that while there has been a loss of nitro radicals in the cellulose molecules there has been only a slight loss of bonds between the cellulose molecules themselves which constitute the yarn, a result quite opposite to that resulting from the normal saponification.

As an example of a method of carrying out our invention, we give the following:

Example Skeins of cellulose nitrate were extracted to remove lubricants, dried at 100 C. and weighed. These skeins were then conditioned in normal atmosphere and then suspended in a large aspirator connected with a flask containing an aqueous solution of ammonia of 28% strength. The aspirator was sealed and a very thin layer of ammonia solution maintained on its base. About every hour during the first eight hours ofreaction. the skeins were shaken out and turned. The temperature in the aspirator was maintained at 27 C. to 29 C. The yarn employed was 150 denier and contained 26 filaments and had an approximate nitro value of 51.7%.

At the end of 2 hours, cellulose nitrate treatedas above was found to be saponified 1.15%; at the end of 5 hours, 5.1%; at the end of 7 hours, 31.7%; at the end of 8 hours,

63.1%; at the end of 10 hours, 97 2% at the the percentage of saponification exceeded 7 more pliable. This is desirable for yarns of.

cellulose ester material since it renders them more suitable for use in the various textile operations. This is especially true of nitro esters of cellulose.

The following table shows the percentage regain of moisture of cellulose nitrate after saponification.

Per cent sa- Per cent poniflcation regain Blank--none 2. 82 58 2. 94 1. 15 3. 20 1. 71 3. 51 2. 5 4. 03 5. 1 4. 75 10. 1 5. 89 31. 7 7. 62 63. 12 8. 54 97. 2 9. 45

The resistance-of the cellulose nitrate material to heat is very largely increased.

treating taining inorganic esters '0 comprises subjecting the same to the action 'lose nitrate.

Whereas the materialcin its or' al' condition could not safely be subj to ironing, even at comparatively low temperatures, the saponified material can be safely ironed at temperatures as high as 260 C. without any danger of inflammability and without any deleterious efiect on the cellulose material.

While the specific description has dealt largely with cellulose nitrate, the invention is not to be considered as limited thereto but as applicable to all inorganic esters of cellulose and the term inorganic cellulose esters as used in the claims is to be so interpreted. The term of saponification as used in the description and'claims is calculated on the loss in dry weight and is quoted as of nitro groups lost, assuming an original nitro value of51.7

Having described our invention what we is: I c

1. Process of saponifying inorganic esters of cellulose which comprises subjecting materials containing the same to the action of a saponifying agent in vapor form under such conditions as to at least partially saponify e cellulose'esters and in the presence of moisture.

claim and desire to secure by Letters Patent material with a saponifying agent vapor form under such conditions as to at least partially saponify the cellulose nitrate and in g the presence of moisture.

9. Process of increasing the tensile strength of .materials containing cellulose nitrate which comprises sapomfying the cellulose nitrate material in an atmosphere gontaining ammonia and moisture in vapor 10. Method of treating textile material containing filaments of inorganic esters ofcellulose comprising at least partially saponifying the inorganic esters of cellulom with a saponifying agent in vapor form in the'presence of moisture.

11. Method of treating textile material con- I taining filaments of cellulose nitrate comprising at least partially sa nifying the cellulose nitrate with a saponi 'ng agent in vapor form in the presence of moisture.

In testimony subscribed our names.

CAMILLE DBEYFUS.

2. Process of saponi materials conslaiponifying agent in the presence 0 oisre g 3. Process of saponifying materials containing cellulose nitrate which comprises the same with a vaporous saponifymg agent in the presence of moisture. 4. rocess of materials concellulose which of an atmosphere containing ammonia and water vapor, the amount of ammonia present 1 being suflic'ient at least partially to saponify the inorganic esters of cellulose.

of saponifying materials contam ng cellulose nitrate which comprises subjectingthe same to the action of. an atmos- WILLIAM WHITEIEAD.

whereof, we have hereunto phere containing ammonia and water vapor,

sum-

the amount of ammonia present being partially to saponify the cellucient at least a. Process of saponifying materials: containing cellulose nitrate which comprises sub-' ectingthe same the action of an atinosphere resultingfrom the.vaporization of a v 28% aqueous solution of ammonia.

- 7. Process of sapon'ifying materials con- I taining cellulose nitrate whichcomprises subjectiagthe "same, at temperatures not above 30 .,;to'the'action of an atm sulting from the vaporization o a 28% aqueous solution of ammonia.

8. Process 'oi incre the tensile strength of cellulose nitrate materials which comprises saponifying the cellulose nitrate here re 

